Global analysis on the decay of DPH (1,6-diphenyl-1,3,5-hexatriene) in isotropic solvents vs temperature and of DPH in phospholipid multilamellar vesicles (MLV) of various composition. Measurement and analysis of the dipolar relaxation of Laurdan (6-dodecanoil-d-dimethylamino naphtalene) in phospholipid MLV of single or mixed phase.